Evolution of crystal structures and electronic properties for TiS2 at high pressure

Using the swarm structure searching technique in combination with density functional theory, we have extensively investigated the crystal structures of TiS2 in a wide pressure range. Our prediction identifies the hexagonal close packed cadmium iodide structure with P-3m1 symmetry is most stable at ambient conditions. An orthorhombic structure with Immm space group is predicted to be energetically much superior to previously proposed orthorhombic cotunnite-type phase in the pressure range from 9.5 to 52.1 GPa, and then I4/mmm is the thermodynamically stable structure above 52.1 GPa. Our calculated results of phonon dispersions have confirmed the dynamical stability of the current predicted Immm and I4/mmm phases. The theoretical electronic band structures and Fermi surfaces reveal pressure-induced electronic topological transitions in P-3m1 and I4/mmm phases, while it is absent in Immm structure. (C) 2018 Elsevier B.V. All rights reserved.